The present invention relates to a recording medium detecting apparatus and a recording medium detecting method. More specifically, the present invention relates to techniques which differentiate two different recording media distinguished by two different coercive forces.
Recording media, such as magnetic cards, having magnetic recording portions with different coercive forces, e.g. a magnetic strip, have been standardized. For example, in addition to conventional low coercive force cards standardized by JIS and ISO, ISO has newly standardized high coercive force cards of 2500 to 4200 Oe: (Oersted). Those high coercive force cards are advantageous in terms of protecting magnetic data recorded on magnetic cards. As a result, the tendency is to switch the low coercive force cards to the high coercive force cards; hence, both kinds of cards may be used together.
Generally, in the case of using magnetic cards with different coercive forces, appropriate write current corresponding to each coercive force must be used for writing in order to obtain an appropriate output. Therefore, a magnetic card reader and the like must comprise a function to determine whether a magnetic card inserted through a card insertion slot is a low coercive force card or a high coercive force card. Hence, a method to determine the coercive force of a magnetic strip on a magnetic card using a permeability sensor is considered. This permeability sensor provides a signal indicating the difference in the permeability of the magnetic strip and the permeability of a space without the magnetic strip. Since there is known relation between the permeability and the coercive force, the output from the permeability sensor can provide a basis for determining whether the magnetic card is a low coercive force card or a high coercive force card.
Inventors of the present invention concluded that, in the case of determining whether a magnetic card is a low coercive force card or a high coercive force card based on the output from the permeability sensor, as described above, the difference between the permeability of the magnetic strip on a low coercive force card and the permeability of the space without a magnetic strip is relatively large (10% and more) wherein the difference between the permeability of the magnetic strip on a high coercive force card and the permeability of the space without a magnetic strip is a small (less than 1%); therefore, it would be difficult to detect low coercive force cards and high coercive force cards merely based on the output from the permeability sensor.
Also, it is preferable that the permeability sensor contacts the magnetic strip of a magnetic card during its use. However, if the permeability sensor is simply placed in the path through which the magnetic card is transferred, the magnetic card tends to be pressed against the permeability sensor or dislocated therefrom during reading/writing of magnetic data. The speed of the magnetic card to be transferred is slightly altered at the moment when the permeability sensor contacts or is separated from the magnetic strip; this is a negative effect on reading/writing of the magnetic data. The above effect of the permeability sensor on the reading/writing process of the magnetic data should be considered.
The present invention intends to provide a recording medium detecting apparatus and a recording medium detecting method which can detect a low coercive force card and a high coercive force card by using a permeability sensor.
Further, the present invention intends to provide a recording medium detecting apparatus which appropriately performs reading/writing of magnetic data by using the permeability sensor and which allows flexibility in design.
Disclosed is an apparatus for detecting a recording medium such as a magnetic strip on a card. When the card is inserted into a card receiving slot, a magnetic head detects the magnetic strip. When the magnetic strip is present and properly placed, a shutter is opened so that the card can proceed further. A permeability sensor is employed in addition to the magnetic head to provide an output signal that is a function of the permeability of the magnetic strip. When the magnetic strip has a high coercivity and thus a relatively low permeability somewhat similar to the permeability of air, the output signal from the sensor is low. When the permeability of the magnetic strip is relatively high (representing low coercivity) the result is a magnetic field unbalanced which provides a substantial output signal.
By determining whether or not the output signal is significantly above or significantly below a particular threshold, a determination can be made that the magnetic strip is either high coercivity or low coercivity and the subsequent read or write operations can be appropriate to that coercivity.
This detection technique is particularly valuable in a context where there are substantially only two types of cards. With respect to the permeability or coercivity of the magnetic strip; one type being a relatively high coercivity, low permeability magnetic strip card and the other being a relatively low coercivity, high permeability magnetic strip card.